For many years, graphite furnace atomic absorption spectrometry (GFAAS) has been recognized as one of the most sensitive analytical techniques for elemental analysis, see W. Slavin, Trends in Analytical Chemistry, 6, 194 (1987). GFAAS sensitivity is primarily due to the high efficiency of analyte transport into the observation volume and the relatively long residence time of the analyte in this volume. It has been found that both temporal and spatial isothermal atomization are required in order to control the effects of gas phase interferences. The use of stabilized temperature platform furnaces (STPF), capacitive current heating, probe insertion, and constant temperature furnaces have made the GFAAS capable of trace element determinations for an increasing variety of complex samples. In spite of these advances, chemical interferences continue to limit the effectiveness of GFAAS and, more importantly, the method is essentially a single element technique.
In the past, several approaches have been used to enhance the graphite furnace as a multielement source for atomic emission spectrometry (AES). D. Littlejohn and J. M. Ottaway, Analyst 104, 208 (1979) have described carbon furnace atomic emission spectrometry (CFAES) which is a sensitive technique for trace analysis using thermal excitation from normal furnace heating. This method is limited by the maximum temperature of the graphite furnace and is not very suitable for elements with high excitation energies.
Falk and his co-workers in H. Falk, E. Hofmann, I. Jaeckel and Ch. Ludke, Spectrochim. Acta 34B, 333 (1979) and H. Falk, E. Hoffmann, and Ch. Ludke, Spectrochim. Acta 36B, 767 (1981), developed a low pressure glow discharge inside the graphite furnace. This technique has been termed FANES (Furnace Atomization Non-thermal Excitation Source). Detection limits for FANES are generally similar or superior to those of GFAAS. The technique is attractive due to its large linear dynamic range, narrow atomic linewidth, multielement capability, and because there is the possibility for independent optimization of atomization and excitation.
Recently, Harnley et al. in J. M. Harnley, D. L. Styris and N. E. Ballou, Abstracts, The Pittsburg Conference & Exposition, Paper No. 847 (1989) have described a similar device in which the graphite furnace serves as an anode of a glow discharge where the cathode is a graphite pin which runs down the centre of the furnace. This design is more flexible in terms of the electrical isolation requirements. This device has been used as an atomic emission source for the analysis of metals and nonmetals. Both of the latter sources are essentially low pressure, direct current (dc) glow discharges. In a glow discharge the gas temperature is low (not in local thermal equilibrium), the residence time of analyte atoms is relatively short, analyte density in the gas phase is low, and perhaps most important from an analytical standpoint, it is not convenient to change samples at low pressure.